The present invention relates to fluid inflatable elements and, more particularly, to inflatable packers which can be easily formed from readily available tubular members such as a section of well casing or the like.
Basically, an inflatable packer consists of a central tubular member or mandrel having an expandable sleeve thereon, the sleeve being connected at each end to spaced annular heads or collars which surround the tubular member. Typically, one of the heads is secured to the tubular member while the other head is free to slide to permit expansion of the sleeve by the application of fluid pressure in the well known manner.
Many types of inflatable packers and methods of constructing same are shown in the prior art. Thus, for example, U.S. Pat. Nos. 2,177,601 to Smith, 3,437,142 to Conover and 3,837,947 to Malone all show various inflatable packers or elements, or methods of forming same. None of the cited patents, which applicant considers to be the most pertinent to the present invention, show an inflatable packer construction which can utilize a readily available tubular section such as a section of well casing or the like to form a packer without the need for welding or relatively extensive machining. Thus, for example, the Smith and Malone patents show packers or inflatable elements wherein at least one of the heads or collars used in the packer construction is secured to the casing or central tubular member by welding. On the other hand, the Conover patent discloses an external casing packer in which the fixed head of the packer is secured to the casing by means of an intermediate threaded collar, threaded both to the head and to the casing.
The types of packer construction described above employing welding and/or a multiplicity of expensively machined parts suffer from several inherent disadvantages. In the case of packers constructed so that one of the packer heads is welded to the central, tubular member, metallurgical problems can arise. Today's deeper and deeper wells require the use of materials in casing, pipe and downhole tools, which can withstand extremely high pressures, corrosive conditions and extreme stresses. Accordingly, it is essential, when a component is to be used in such deep well environments, to ensure that any welded connections be stress relieved to ensure that the welded joint will not fail. Even when only metal components are involved, stress relieving the welded joint may present a problem since it requires special annealing or heat facilities. The need for such facilities virtually precludes on site construction of inflatable packers. However, even if such stress relieving facilities are available, there is a problem in the case of inflatable packers because the heat treating or annealing required to stress relieve the welded joints will damage, if not destroy, the elastomeric material used in forming the inflatable element. Thus, it is quite difficult, if not impossible, to stress relieve an inflatable packer having an elastomeric, expandable element once the packer has been completely constructed.
In the case of packers utilizing threaded connections to secure one of the packer heads to the central tubular member or mandrel, the difficulties are apparent. Such connections require relatively extensive machining and are, accordingly, expensive to manufacture. Again, the need for such machining makes it difficult, if not impossible, to construct the packers in the field.